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Hyper-threading Technology (HTT) Default for new Intel high end chips One ALU Duplicate state of computation (registers) to create two logical processors (chip size *= 1.05) Parallel instruction preparation (decode) ALU should see ready work more often (provided there are two active threads)

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Theory vs practice “In theory, there is no difference between theory and practice. In practice, there is no relationship between theory and practice.” Grant Gainey “The gap between theory and practice in practice is much larger than the gap between theory and practice in theory.” Jeff Case

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Summary Hyper-threading is … Abstraction (modelling) leverages information: you can often understand a lot even when you know very little r = s/(1-U) is worth remembering You do need to connect theory and practice – and practice is harder than theory Questions?